Resource constraint measures in a dual constrained job shop

Over the last couple of decades scheduling in the dual constrained job shop has been extensively studied by researchers. Previous scheduling research on dual constrained job shops has assumed that both the resources uniformly constrain the system. However, practice has shown that in job shops, due to the varying product mix, the resource constraining the system changes over time. Also, the interaction of the constraining resources affects shop performance to a much greater degree that the effect caused by either individual constraint. The importance of scheduling based on the resource constraint has been discussed by [2]. Previous literature has not presented any techniques by which to identify the resource constraining the system. In this paper, based on a review of the previous literature, alternative indices are developed to measure the degree to which constraints are operative in the dual constrained job shop. The alternative indices of resource constraint are used in a shop loading algorithm in order to study which of the two measures is a better indicator of resource constraint. A simulation study suggests there may be no major differences in the two indicators of resource constraint with respect to improving shop performance (i.e. root mean squares of tardiness and average job flow time).